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changes.go
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changes.go
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
package pouchdb
import (
"context"
"encoding/json"
"fmt"
"io"
"sync"
"github.com/gopherjs/gopherjs/js"
"github.com/go-kivik/kivik/v4/driver"
"github.com/go-kivik/pouchdb/v4/bindings"
)
type changesFeed struct {
changes *js.Object
ctx context.Context
feed chan *driver.Change
errMu sync.Mutex
err error
lastSeq string
}
var _ driver.Changes = &changesFeed{}
func newChangesFeed(ctx context.Context, changes *js.Object) *changesFeed {
feed := make(chan *driver.Change, 32)
c := &changesFeed{
ctx: ctx,
changes: changes,
feed: feed,
}
changes.Call("on", "change", c.change)
changes.Call("on", "complete", c.complete)
changes.Call("on", "error", c.error)
return c
}
type changeRow struct {
*js.Object
ID string `js:"id"`
Seq string `js:"seq"`
Changes *js.Object `js:"changes"`
Doc *js.Object `js:"doc"`
Deleted bool `js:"deleted"`
}
func (c *changesFeed) setErr(err error) {
c.errMu.Lock()
c.err = err
c.errMu.Unlock()
}
func (c *changesFeed) Next(row *driver.Change) error {
c.errMu.Lock()
if c.err != nil {
c.errMu.Unlock()
return c.err
}
c.errMu.Unlock()
select {
case <-c.ctx.Done():
err := c.ctx.Err()
c.setErr(err)
return err
case newRow, ok := <-c.feed:
if !ok {
c.setErr(io.EOF)
return io.EOF
}
*row = *newRow
}
return nil
}
func (c *changesFeed) Close() error {
c.changes.Call("cancel")
return nil
}
// LastSeq returns the last_seq id, as returned by PouchDB.
func (c *changesFeed) LastSeq() string {
return c.lastSeq
}
// Pending returns 0 for PouchDB.
func (c *changesFeed) Pending() int64 {
return 0
}
// ETag returns an empty string for PouchDB.
func (c *changesFeed) ETag() string {
return ""
}
func (c *changesFeed) change(change *changeRow) {
go func() {
defer func() {
if r := recover(); r != nil {
_ = c.Close()
if e, ok := r.(error); ok {
c.err = e
} else {
c.err = fmt.Errorf("%v", r)
}
}
}()
changedRevs := make([]string, 0, change.Changes.Length())
for i := 0; i < change.Changes.Length(); i++ {
changedRevs = append(changedRevs, change.Changes.Index(i).Get("rev").String())
}
var doc json.RawMessage
if change.Doc != js.Undefined {
doc = json.RawMessage(js.Global.Get("JSON").Call("stringify", change.Doc).String())
}
row := &driver.Change{
ID: change.ID,
Seq: change.Seq,
Deleted: change.Deleted,
Doc: doc,
Changes: changedRevs,
}
c.feed <- row
}()
}
func (c *changesFeed) complete(info *js.Object) {
if results := info.Get("results"); results != js.Undefined {
for _, result := range results.Interface().([]interface{}) {
c.change(&changeRow{
Object: result.(*js.Object),
})
}
}
c.lastSeq = info.Get("last_seq").String()
close(c.feed)
}
func (c *changesFeed) error(e *js.Object) {
c.setErr(bindings.NewPouchError(e))
}
func (d *db) Changes(ctx context.Context, options map[string]interface{}) (driver.Changes, error) {
changes, err := d.db.Changes(ctx, options)
if err != nil {
return nil, err
}
return newChangesFeed(ctx, changes), nil
}